# Activities

• • • ##### Subject Area

• Math: Geometry: Triangles

• ##### Author 9-12

60 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition
• ##### Software

Cabri Geometry™
TI Connect™

• ##### Accessories

TI Connectivity Cable

• ##### Other Materials
This is Activity 4 from the EXPLORATIONS Book:
Exploring The Basics Of Geometry With Cabri

## Isosceles Triangle

#### Activity Overview

In this activity, students construct isosceles and equilateral triangles. They discover that if two sides of a triangle are congruent, then the angles opposite them are congruent. They understand that an equilateral triangle is also equiangular.

#### Before the Activity

Install the Cabri™: Jr. App on the students' graphing calculators using one of these two methods:

• TI-Connect™,  a TI Connectivity Cable, and the Unit-to-Unit Link Cable
• TI-Navigator™  "send to class" feature
• See the attached PDF file for detailed instructions for this activity
• Print pages 15 - 16 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to the class.

• Construct an isosceles triangle
• Measure and label segments and angles of the triangle
• Identify the sides and angles that are congruent
• Verify this relationship with different isosceles triangles
• Observe that if two sides of a triangle are congruent, then the angles opposite them are congruent
• Create an equilateral triangle using the Regular Polygon feature
• Measure the angles
• Observe that if all sides of a triangle are equal, then the triangle is equiangular
• Alter the triangle and verify if the relationship holds true for all equilateral triangles
• #### After the Activity

Review student results:

• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary